Method for heat treatment of worn tires and other rolling bodies of steel



April 13, '1937. A G. E. HULTGREN 2,076,992

METHOD FOR HEAT TREATMENT OF WORN TIRES AND OTHER ROLLING BODIES OF STEEL Filed May 28 1935 rm %&

Patented Apr. 13, 1937 *M'E'rnon FOR I TIRE-SAND OT STEEL PATENT HEAT TREATMENT OF WORN ROLISING counts on treads of railroad and street car wheels and tires becometunevenly worn during service and": have" therefore to be: restored from time to timeto thecorrect prcfileby machining. In case ofistee1 thissisusually done by turning. In doing so, however. very hard. spots are. often encountered whiche originate from occasions. in service when, owing to heavy braking, the Wheels have ceased? torotate and: have slipped on the rails. The heat of friction then brings the spot of contact up to such a high temperature-past the transformation temperature A01-th3,t the subsequent cooling causes the steel adjacent to it to harden to glass hardness. When such hard it spots are present the turning must be taken so deep that the point of the cutting tool works beneath the bottom of any hard portions. If such cuts are not taken the lathe will be subjected to severe strain and the cutting edge of the tool will be quickly ruined. In other words, the presence of such hardened spots is the cause of increased cost in turning and, at each re-turning operation, necessitates the removal of a layer of steel, that might otherwise be usefully retained. According to the present invention the treads of the worn wheels or tires are before re-turning subjected to a heating operation so as to anneal or temper any hard spots present to a moderate and suitable hardness. In this way the treads may be re-turned at a normal speed of machining and the cut need only be taken so deep as to clean the most worn part.

The heating may be carried out in various ways. Below is described a method that has been found to be very suitable. The pair of wheels is mounted on a device which imparts to it a slow rotation. At one point of the circumference a concentrated source of heat, for instance a burner for acetylene and oxygen, is placed, which is of such design and dimensions that the worn tread is heated over its whole width or that part of it which is to be heat-treated. Through experiment the speed of rotation and the adjustment of the heat supply are found which bring about sumcient annealing or tempering effect in a sulficiently deep surface layer without causing such overheating as will impair the wear resistance of the steel. After one revolution the process is stopped and the wheels can be turned after complete or only partial cooling, as desired, without quenching.

During rotation the pair of wheels may be mounted on centers or otherwise the journals or the wheels may rest on rollers or wheels or the pair of wheels may be given a slowly rolling 1 Claim. (cums-21:5)

movement on rails or guides supporting .tha wheels or journals;v In the latter. case: the; heat:- ing device follows" the. translational movement; ofthe'pair'of-wheels; 2 1 I The accompanying. drawing illustrates a: device 5 for-"treating a railroad; car wh'eel according to: the? inventiongin. which the. wheel: rests on two: rolls l in such' a manner that-it: may be. put into rota-e: tion and at the top there is mountedta cap Land. a number of burners 6.

Figure 1 shows the device from one side with the cap 2 in section.

Figure 2 shows the device seen in perpendi'cwlar direction and also with the cap in section.

Figure 3 is a top view of the device the cap 2 being removed. 7

The cap 2 of refractory material or provided with refractory lining is so shaped that together With the tread 3 and the flange 4 it forms a channel 5. The cap is placed immediately in front of a row of burners 6, which are directed in an oblique angle to the tread and to the cap, so that the flame will enter the channel and heat the cap, which in its turn will heat the part of the tread enclosed by the same. By turning the tire the part of the tread, which is inside the 'cap, will be caused to move towards the hottest part of the flame and thus the tread will be pre-heated before reaching the said part of the flame. In this way the supply of heat is economized.

As will be seen from Figure 3 the burners 6 are in the embodiment shown arranged in a transverse row in order to distribute the heat over the desired width of the tread and to heat also the flange in the same way. In order that the heating shall be uniformly distributed the burners may be given an oscillating motion in the transverse direction as shown by arrows.-

By arranging two burners or sets of burners in succession at a suitable distance the depthto which the heat penetrates the steel may be increased without danger of overheating or burning the surface of the tread.

The penetration may also be increased and the cooling of the heated surface retarded by applying behind the burner or burners, and near to the heated tread, an insulating shield of refractory material, asbestos or the like, which shield serves to minimize radiation.

Instead of oxy-acetylene flames electric arcs or other sources of heat of high temperature may be used for heating the tread. Also electric current may be conducted through the surface layer of the tread by the use of two adjacent sliding contacts or brushes. 55

In certain cases it may be suitable to heat the wheels or tires in the lathe where they are turned, either by completing the heating operation before turning or by letting the heating device and the cutting tool operate simultaneously arranged in series in the same plane normal to the axis of rotation. Cooling, by air-blast, oil, water or the like, may be applied between the two.

By the use of the heat treatment described the worn treads of wheels or tires may be softened sufliciently to enable rough-turning to be carried out at twice the usual speed without unduly straining the lathe or the cutting tool. In this way the production of the lathe is doubled and the cost of turning correspondingly reduced.

It has already been pointed out that in turning worn wheels or tires with hard spots as heretofore practised the cut is taken so deep that the point of the cutting tool is brought to work beneath the bottom of the hard spots. This disadvantage is obviated in turning wheels or tires treated as described thus effecting a saving of a layer about 2 millimeters thick at each .re-turning operation with a corresponding increase in the life of the wheels or tires. The cost of the treatment is comparatively small as compared with the aggregate saving in cost of machining and of material.

The process is not limited to railroad and street car wheels. It may also be used for other rolling bodies of steel that have been subjected to heating by friction sufficient to cause hardening of the surface.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

Method for treating worn tires and other rolling bodies of steel which are to be returned, comprising subjecting the material of the tread of the body, without heating the whole body, to a heating treatment with subsequent cooling without quenching, the heating being effected at such a temperature that hardened worn spots are softened, thereby enabling the tread to be turned without difliculty, the method being distinguished by effecting the heating by a flame directed against the tread in a plane at right angles to the axis of the body and passing through a channel formed between a circumferential part of the tread and a refractory cap enclosing the said part, the rolling body being rotated and the part of the tread, which is inside the cap, being there by caused to move towards the hottest part of the flame, so that the tread will be pre-heated before reaching said part of the flame.

AXEL GUSTAF EMANUEL HULTGREN. 

